The Electro Magnetic Calorimeter (EMCal) enhances the capabilities of ALICE to measure highly energetic  photons, electrons, neutral pions, and jets of particles, and the correlations between them.The EMCal is a shashlik-type lead-scintillator sampling calorimeter comprising 4416 individual modules that are grouped into twenty Super Modules (SM). Each of the modules is composed by 4 optically isolated towers, resulting to 17664 individual towers in total.  The optical readout of each tower is provided using wavelength shifting fibers coupled to an Avalanche Photo Diode (APD).

The overall design of the calorimeter is heavily influenced by its integration within the ALICE setup and SM’s of 3 different sizes are used: full-, 2/3- and 1/3- size.  Each full-size SM is assembled from 1224= 288 modules. Each 2/3-size SM is assembled from 1216=192 modules, and each one-third size SM is assembled from 424=96 modules.

The EMCal is made of 10 full-size SMs and 2 1/3-size SMs covering ||<0.7 in pseudo-rapidity  and 80 <  < 187 in azimuth.  The addendum of EMCal, so called DCal, is made of 6 2/3-size SMs and 2 1/3-size SMs with acceptance:  0.22 < || < 0.7, 260 <  < 320 and || < 0.7, 320 <  < 327.  The EMCal and the DCal are placed in two independent regions in azimuth, as illustrated in Figure 2. The SMs are located  4.5 m in radial distance from the beamline, inserted into support frames situated between the Time-of-Flight  detector and the ALICE L3 magnet. The weight of a single full-size SM is  7.7 tons, and the total weight of all 20 SMs is  120 tons. 

The front face dimensions of the towers are ~66 cm2 resulting in individual tower acceptance of ∆η∆  0.0140.014 at η=0. The towers are arranged within the SMs such that each tower is approximately projective in η and   to the interaction vertex. The towers are operated at ~25C ambient temperature with a nominal APD gain of 30, allowing to achieve a 14-bit effective dynamic energy range from 16 MeV to 250 GeV per tower. The signal time is also measured per tower with few ns precision.  

Both EMCal and DCal are also equipped with triggering systems. The signals of 44 groups of adjacent towers are summed up and a peak finding algorithm is used to find a signal peak, providing L0- and L1- level triggers to the ALICE Central Trigger Processor allowing to select online high energy objects like photons and electrons.  The signals from 1616 and 3232 adjacent towers also processed and a L1-level trigger is provided for detecting wide objects as jets. In order to reduce the bias due to multiplicity fluctuations in heavy-ion collisions, there is a direct communication between EMCal and DCal L1 triggering units for considering the underlying event background in the online L1 trigger decision.

 

EMCAL

Documents:

  • ALICE Collaboration, P. Cortese et al, ALICE electromagnetic calorimeter technical design report (2008) CERN-LHCC-2008-014 (ALICE-TDR-014).
  • ALICE DCal: An Addendum to the EMCal Technical Design Report Di-Jet and Hadron-Jet correlation measurements in ALICE (2010)   ALICE-TDR-14-add-1
  • H. Muller et al, Configurable electronics with low noise and 14-bit dynamic range for photodiode-based photon detectors, Nucl. Instrum. Meth A565 (2006) 768–783
  • J. Kral et al,  L0 trigger for the EMCal detector of the ALICE experiment, Nucl. Instrum. Meth. A693(2012) 261–267
  • O. Bourrion et al, The ALICE EMCal L1 trigger first year of operation experience, JINST 8 (2013) C01013
  • ALICE Collaboration, U. Abeysekara et al, ALICE EMCal Physics Performance Report, arXiv:1008.0413.
  • ALICE Collaboration, Performance of the ALICE Electromagnetic Calorimeter, in preparation.

EMCAL Internal:

Photo Galleries:

 

  • Project Leader: Constantin Loizides (Oak Ridge National Laboratory - (US))

  • Deputy Project Leaders: Thomas Cormier (Oak Ridge National Laboratory - (US)) and Christophe Furget (Centre National de la Recherche Scientifique (FR))

  • Technical Coordinator: Martin Poghosyan (Oak Ridge National Laboratory - (US))

Participating Institutes:

  • California Polytechnic State University, San Luis Obispo, CA 93407, USA
  • CCIN2P3, Lyon, France
  • CERN, European Organization for Nuclear Research, 1211 Geneve, Switzerland
  • Creighton University, Omaha, NE 68178, USA
  • INFN Laboratori Nazionali di Frascati, 00044 Frascati, Italy
  • Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
  • Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA
  • LPSC, University Joseph Fourier Grenoble, CNRS/IN2P3, Grenoble, France
  • Oak Ridge National Laboratory (ORNL), Oak Ridge, TN 37831, USA
  • SUBATECH, Ecole des Mines, Universite de Nantes, CNRS/IN2P3, Nantes, France
  • Institute of Physics, University of Tsukuba, Japan
  • University of Houston, Houston, TX 77204, USA
  • University of Jyvaskyla, Jyvaskyla, Finland
  • University of Tennessee, Knoxville, TN 37996, USA
  • University of Texas at Austin, Austin, TX 78702, USA
  • Wayne State University, Detroit, MI 48201, USA
  • Yale University, New Haven, CT 06511, USA
  • IHEP, Protvino, Russia
  • Niels Bohr Institute, Copenhagen, Denmark
  • Purdue University, West Lafayette, IN 47907, USA
  • NIKHEF, Amsterdam, Netherlands
  • Universidade Estadual de Campinas, Campinas, Brazil
  • Universidade de Sao Paulo, Sao Paulo, Brazil
  • Sezione INFN, Catania, Italy
  • Universita Catania e Sezione INFN, Catania, Italy
  • Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma, Italy
  • IPHC, Universite Louis Pasteur, CNRS-IN2P3, Strasbourg, France
  • Valencia Polytechnic University, Valencia, Spain
  • University of Valencia, Valencia, Spain
  • Hua–Zhong Normal University, Wuhan, China

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